The Ottawa free trader. [volume] (Ottawa, Ill.) 1843-1916, 1887-10-22
Making Plate Glass.

There has been considerable talk OF a
plate glass works In Ottawa; and the hope
that one will yet be secured is not yet rele.
gated to the debris Of impotent dreams by
any means, but is now, at least, keeping
company with other "hopes deferred" the
ccomplshment of which Is o feat for the
future.
Meantime, few probably know bow plate
glass is made. The following description
of the process in practice at Creighton,
some 20 miles north of Pittsburgh, will,
therefore, not be undressing 1t is taken
from lecture on GLASS" which we find
In Building. The advantage Ottawa might
have In the manufacture of plate glass lies
entirely in the use OF water power for
grinding, which, as will be seen on reading
the extract, requires an enormous plant for
power. Should the Illinois river be i'm.
proved to furnish that power, Ottawa could
compete with all the world on plate glass,
in spite of the advantage of natural gas.
The extract is as follows:
The glass itself has the same constitution
as sheet glass. 1t Is simply double sill
cate of lime and soda. The melting is
carried out In large, open pots, the furnaces
differing In their construction from those
already described only in their greater size
and the substitution of doors made of ire
clay tiles set in cast.iron frames for the
usual gathering holes. When the fusion
has been completed the door opposite the
PCT is opened, and twopronged fork,
mounted on wheels, Is Inserted into the
furnace. The distance between the prOngs
is sufficient to permit them to pass into de-
pressions made in each side of the melting
pot. and thus secure II In firm grasp. BY
this method the pot Of molten glass Is re-
moved from the furnace, and Is carried on
low truck TO the casting table. At Creigh-
ton, the casting house. containing furnaces,
tables, and annealing ovens, Is 65Ox16O feet,
about four times as large as the famous
halle of st. Gobian, in France, and nearly
double the size of the British Works al
Ravenhead. There are two casting tables
at Creighton, seven inches thick, nineteen
feet long, and fourteen feet wide. Each Is
provided with an iron roller thirty inches
in diameter and fifteen feet long. Strips of
iron on each side of the table afford bear.
ing for the rollers, and determine the thick
ness of the plate of glass. The tables are
mounted on wheels, and run on q track
which reaches every furnace and anneal
ing oven. The table having been brought
as near as possible to the melting furnace
the pot of molten glass is lifted by means
of a crane, and Its contents quickly poured
on the table, the heavy iron roller Is then
passed from end to end, spreading the
glass into layer of uniform thickness
As rapidly as possible the door OF the an.
healing oven Is opened, and the plate of
glass introduced. The door Is then closed,
and the glass left TO anneal. All of these
operations are performed In little more
time than II takes to describe them, as II Is
desirable to get the glass into the annealing
oven as hor as can be. A large number of
ovens are required for annealing purposes,
as the glass must remain several days to
cool. When the glass Is taken out its sur.
face Is found to be decidedly rough and
uneven. A small quantity is used In this
condition for sky-lights and other purposes
where strength is required without trans.
parency. 1t Is known In the market as
rough plate. The greater part of the glass
is ground, smoothed, and polished before l,
leaves the works. The grinding Is accom-
plished by means of rotary grinding ma
chimes, the abrading material being com.
mon river sand dredged from the ALE
ghany. Three million bushels are required
annually for this purpose. The plates are